The present invention relates to a method for preparing a specimen from a cellular suspension of biological cells. In particular, the invention relates to a method for preparing a specimen comprising a uniform distribution of biological cells on a substrate surface.
The collection or preservation of biological cells in fluid suspension is common in medicine and biology for the detection of disease. For example, naturally voided urine contains urothelial cells from the lining of the bladder. If the urothelial cells are separated from the urine and then placed on a substrate surface, such as a microscope slide, examination of the cells can determine the presence or absence of certain diseases. Another example is the PAP Smear Test which involves the artificial exfoliation of epithelial cells from the cervix of the uterus and the subsequent suspension of the exfoliated epithelial cells in a water/alcohol solution to preserve and protect the cells. If the epithelial cells are separated from the solution and then deposited on a microscope slide, examination of the cells can determine the presence or absence of precancerous lesions on the cervix.
However, current techniques for the preparation of specimens from cellular suspensions are deficient since the cellular suspensions may contain debris and contaminants which can interfere with the examination of the desired (xe2x80x9ctargetxe2x80x9d) cells. For instance, in the case of cervical epithelial specimens, the contaminants may include leukocytes, erythrocytes, bacteria and mucus. In addition, the typical specimen may contain several layers of cells and/or the cells may overlap one another, thereby rendering the detection of cell abnormalities difficult. Another reason is that, for the Pap test or indeed any other type of test requiring an exfoliation instrument, the technique of transferring the collected cells from the exfoliation instrument to the glass slide can be very inefficient. In some studies it has been shown that less than 20% of the collected sample is effectively transferred. By contrast, a liquid-based specimen allows, as a preliminary step, all of the collected cells to be rinsed or washed off of the exfoliation instrument into the collection fluid thereby improving specimen recovery and aiding in subsequent diagnostic accuracy.
Accordingly, there is a need for a method for preparing specimens from cellular suspensions which enhances the ease and accuracy of evaluation of biological cells for abnormalities.
According to the present invention, there is provided a method and apparatus for preparing specimens from cellular suspensions which enhances the specimen recovery as well as the ease and accuracy of evaluation of biological target cells for abnormalities.
The method comprises the steps of providing a suspension of biological cells in fluid wherein said cells include biological target cells; extracting a portion of the biological target cells from the suspension; distributing the extracted portion over a substrate surface into a primary layer with the remaining extracted biological target cells being located on top of said primary layer; and removing the plurality of cells located on top of the primary layer.
Specimens prepared according to the above method are substantially free of debris and contaminants. In addition, the cells comprising such specimens are densely packed into a single layer with little cell overlap. Therefore, the ease and accuracy of detection of cell abnormalities is greatly enhanced.
In another aspect, the present invention provides an apparatus for preparing a biological cellular specimen on the surface of a substrate, said apparatus comprising: a filter tube including an outlet port and a porous filter medium coupled to the outlet port; a tubular member having an interior region and a pair of opposite ends, and including means for receiving said filter tube within said interior region; and means for sealingly coupling the surface of said substrate to one of the ends of said tubular member.